ABSTRACT

Handling containers with explosive cargo at the port carries a risk of explosion. The resulting fatalities depend on the blast pressure and its reach. Quantitative risk assessment (QRA) evaluates fatality probabilities based on estimated blast pressure. This paper presents a case study of an explosion in a 20 feet ISO container carrying IMDG Class I cargo. Simplistic solutions using analytical shock pulse generation and propagation were employed with explicit solver, where Friedlander equation and experimental models were characterized as blast wave loads. Simulated overpressures and empirical overpressures showed good agreement. The study provides critical input for the estimation of effective risk assessment and safety protocols in hazardous materials transport.

INTRODUCTION

The IMDG Code (International Maritime Dangerous Goods Code), 1972 was established to prevent incidents involving dangerous goods by providing standardized international regulations for maritime transport. The carriage of dangerous goods and marine pollutants on sea-going ships is governed by the International Convention for the Safety of Life at Sea (SOLAS) and the International Convention for the Prevention of Pollution from Ships (MARPOL). The IMDG Code, a legal document, is mandatory for maritime transport of such hazardous materials. Various studies have assessed the risks associated with handling explosive cargo, contributing for understanding and enhancing safety protocols. For example, (DNV, 1994) conducted a QRA study for the Bunbury outer harbour at Marlston Hill using the SAFETI software package. The study assessed risks associated with hazardous materials - import, storage, and transport - handled at the outer harbour to identify any operational restrictions. The harbour was licensed to export up to 2000 tonnes of Ammonium Nitrate, 25 kg of explosives, and Methanol in containers. Various data were collected, including maps of the surrounding area, meteorological data, current and future hazardous cargo shipments, transport routes (including pipelines), and details of Methanol storage, which involved various steps for risk assessment such as site visits, screening, and hazard identification, consequence calculations using the same SAFETI software, frequency analysis, and risk calculations with individual risk results. Then the results were compared against the Environmental Protection Agency (EPA) criteria for acceptable risk. The assessment revealed that the maximum individual risk in the outer harbor was 5 × 10−7 per year,compared to the EPA's acceptable limit of 1 × 10−6 per year. Locking (2013) also presented a study on TNT equivalence, comparing experimental results against predictions for various explosive materials. TNT equivalence was used to compare the performance of different explosives based on the blast field produced (pressure or impulse), heat generated (Q), or detonation velocity (D). Locking compared these methods with experimental data, examining various explosives, propellants, and polymer-bonded explosives (PBX). The study determined that the charge configuration significantly affects TNT equivalence values for both pressure and impulse. This comparative analysis highlighted that the physical arrangement of the charge plays a crucial role in the resultant equivalence values, thereby impacting the predictive accuracy for different explosive materials. Similarly, the UK Health and Safety Executive (H. S. E., 1995) published a report on the risks associated with handling explosives in ports. They considered explosives, pyrotechnical materials, and explosive articles, focusing on obtaining the best estimate values for the risks involved in moving explosives through ports. A risk assessment study compared the risks for ports and a jetty, providing a snapshot in time of the risks based on the volume and type of explosives trade at the time of the study. There was also a study conducted by Chen et al. (2019) on the Tianjin port explosion that occurred on August 12, 2015, at the Ruihai hazardous goods warehouse in Tianjin Port, China. Their paper dwells into the findings of their analysis, utilizing two distinct methods to dissect the Tianjin incident. The objective was to unravel the institutional shortcomings that contributed to both the occurrence and the severity of the event. The explosion involved multiple detonations, resulting in significant damages equivalent to 15 tons and 430 tons of TNT explosives. The stored materials included Nitrocellulose and ammonium Nitrate, as well as flammable, toxic, and corrosive liquid and solid substances. The spontaneous combustion of nitrocellulose led to heat liberation and subsequent ignition. This caused damage to the container, leading to the spillage of a large quantity of hazardous chemicals. As these chemicals reached their explosion temperature, an explosion followed. Manca (2013) also explored the quantitative assessment of safety reports concerning the consequences of solid explosive detonation. The paper introduced analytic and numerical methods crucial for determining these consequences and defining the permissible amount of stored/processed solid explosives. Different detonation scenarios can have varying impacts on surrounding equipment and people, including operators and the general population. Only through quantitative assessment can one accurately identify the most significant effects based on the specific event and surrounding conditions. The methodology outlined in the paper focuses on evaluating solid explosive blast impacts in terms of overpressure and fragment formation. For future work, the author highlighted the need to consider degradation/combustion, thermal radiation, and seismic wave effects resulting from solid explosive detonations.

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